1. Field of the Invention
This invention relates to a plasma display panel, and more particularly to a plasma display panel that is capable of improving a contrast as well as reducing the power consumption.
2. Description of the Related Art
Recently, a plasma display panel (PDP) feasible to a manufacturing of a large-dimension panel has been highlighted as a flat panel display device. The PDP typically includes a three-electrode, alternating current (AC) surface discharge PDP that has three electrodes and is driven with an AC voltage as shown in FIG. 1.
Referring to FIG. 1, a discharge cell of the three-electrode, AC surface discharge PDP includes a scanning/sustaining electrode 12Y and a common sustaining electrode 12Z formed on an upper substrate 10, and an address electrode 20X formed on a lower substrate 18. The scanning/sustaining electrode 12Y and a common sustaining electrode 12Z are transparent electrodes made from indium thin oxide (ITO). Since the scanning/sustaining electrode 12Y and the common sustaining electrode 12Z have high resistance values, first and second bus electrodes 28Y and 28Z are formed at the rear sides of the scanning/sustaining electrode 12Y and the common sustaining electrode 12Z. The first and second bus electrodes 28Y and 28Z receive a driving waveform from a driving waveform supply (not shown) and apply it to the scanning/sustaining electrodes 12Y and the common sustaining electrode 12Z. On the upper substrate 10 in which the scanning/sustaining electrode 12Y is formed in parallel to the common sustaining electrode 12Z, an upper dielectric layer 14 and a protective film 16 are disposed. Wall charges generated upon plasma discharge are accumulated in the upper dielectric layer 14. The protective film 16 prevents a damage of the upper dielectric layer 14 caused by the sputtering generated during the plasma discharge and improves the emission efficiency of secondary electrons. This protective film 16 is usually made from MgO. A lower dielectric layer 22 and barrier ribs 24 are formed on the lower substrate 18 provided with the address electrode 20X, and a fluorescent material 26 is coated on the surfaces of the lower dielectric layer 22 and the barrier ribs 24. The address electrode 20X is formed in a direction crossing the scanning/sustaining electrode 12Y and the common sustaining electrode 12Z. The barrier ribs 24 is formed in parallel to the address electrode 20X to prevent an ultraviolet ray and a visible light generated by the discharge from being leaked to the adjacent discharge cells. The fluorescent material 26 is excited by an ultraviolet ray generated upon plasma discharge to produce a red, green or blue color visible light ray. An active gas for a gas discharge is injected into a discharge space defined between the upper/lower substrate and the barrier rib.
As shown in FIG. 2, such a discharge cell is arranged in a matrix type. In FIG. 2, the discharge cell 1 is provided at each intersection among scanning/sustaining electrode lines Y1 to Ym, common sustaining electrode lines Z1 to Zm and address electrode lines X1 to Xn. The scanning/sustaining electrode lines Y1 to Ym are sequentially driven while the common sustaining electrode lines Z1 to Zm are commonly driven. The address electrode lines X1 to Xn are driven with being divided into odd-numbered lines and even-numbered lines.
Such a three-electrode, AC surface discharge PDP is driven with being separated into a number of sub-fields. In each sub-field interval, a light emission having a frequency proportional to a weighting value of a video data is conducted to provide a gray scale display. For instance, if a 8-bit video data is used to display a picture of 256 gray scales, then one frame display interval (e.g., 1/60 second=16.7 msec) in each discharge cell 1 is divided into 8 sub-fields SF1 to SF8. Each sub-field is again divided into a reset interval, an address interval and a sustaining interval. A weighting value at a ratio of 1:2:4:8: . . . :128 is given in the sustaining interval. Herein, the reset interval is a period for initializing the discharge cell; the address interval is a period for generating a selective address discharge in accordance with a logical value of a video data; and the sustaining interval is a period for sustaining the discharge in a discharge cell in which the address discharge has been generated. The reset interval and the address interval are equally assigned in each sub-field interval.
As shown in FIG. 3A to FIG. 3C, such a PDP is divided into an effective display part 30 in which a picture is to be displayed and a non-display part 32 in which a picture is not to be displayed. The effective display part 30 has a number of discharge cells 1 arranged in a matrix pattern to display a picture. The non-display part 32 is mounted with various circuits for driving the electrodes 12Y and 12Z within the discharge cell 1 so that the discharge cells 1 in the effective display part 30 can display a picture. The scanning/sustaining electrode 12Y and the common sustaining electrode 12Z are extended from the effective display part 30 into the non-display part 32. In this case, the first and second bus electrodes 28Y and 28Z are extended into a longer distance than the scanning/sustaining electrode 12Y and the common sustaining electrode 12Z to receive a driving waveform from the driving waveform supply. A driving waveform is alternately applied to the first and second bus electrodes 28Y and 28Z in the sustaining interval. By the driving waveform applied to the first and second bus electrodes 28Y and 28Z, a discharge is generated at the effective display part 30 and the non-display part 32. In other words, since the scanning/sustaining electrode 12Y and the common sustaining electrode 12Z are extended into the non-display part 32, an undesired discharge is generated at the non-display part 32. Also, a picture is not displayed at the non-display part 32, the barrier ribs 24 and the fluorescent material 26 are not provided. Thus, the non-display part 32 has a discharge space wider than the effective display part 30 to generate a discharge more easily than the effective display part 30.
The conventional PDP as described above has a problem in that, since an undesired discharge is generated at the non-display part 32, it has large power consumption. Also, it has a problem in that its contrast is deteriorated due to a light produced by the discharge at the non-display part 32. Moreover, the conventional PDP has a problem in that, since an electric field concentrates on the corners 34 of the scanning/sustaining electrode 12Y and the common sustaining electrode 12Z formed at the non-display part 32, an insulation breakage in the transparent electrodes may occur.